The Inter Milan star told The Sun: "Nani is a young player with a lot of quality. I was very impressed when I saw him playing for Sporting and Portugal last season.
Everybody knows about Ronaldo but Nani has the same quality.
"It depends how he adapts to a new style of football. It can take time to integrate but he has the quality to be a great footballer.
"I know a lot of the coaches at Sporting. They are the same guys who helped me when I was a kid. We seem to produce a lot of wingers, those sorts of player, in Portugal.
"We have similar qualities to the Brazilians in the way we like to play our football.
"It is the mentality and the philosophy of Sporting Lisbon to produce players like Ronaldo and Nani. They have always produced a lot of talented players because of the way they develop the youngsters as athletes and as men.
"The Portuguese do not have the money to compete with the big clubs in Europe, so must invest in youth."